1. Field of the Invention
The present invention relates, in general, to the packaging art, and, more particularly, is concerned with a continuous reclosable plastic zipper of a type which is used to close the mouth of a bag or package, and which includes a tamper-evident, non-reclosable peel seal with a feature giving a clear indication of the integrity of the peel seal.
2. Description of the Prior Art
In the use of plastic bags and packages, is particularly for foodstuffs, it is important that the bag be hermetically sealed until the purchaser acquires the bag and its contents, takes them home, and opens the bag or package for the first time. It is then commercially attractive and useful for the consumer that the bag or package be reclosable so that its contents may be protected. Flexible plastic zippers have proven to be excellent for reclosable bags, because they may be manufactured with high-speed equipment and are reliable for repeated reuse. A typical zipper is one which has a groove at one side of the bag mouth and a rib at the other side, which rib may interlock into the groove when the sides of the mouth of the bag are pressed together. Alternatively, a member having a plurality of ribs may be on one side of the bag mouth, while a member having a plurality of channels may be on the other side, the ribs locking into the channels when the sides of the mouth of the bag are pressed together. In such a case, there may be no difference in appearance between the two members, as the ribs may simply be the intervals between channels on a strip which may lock into another of the same kind. In general, and in short, some form of male/female interengagement is used to join the two sides of the bag mouth together. The so-called members, or strips, are bonded in some manner to the material from which the bags themselves are manufactured.
Usually, pull flanges extend above the rib and groove strips, which pull flanges may be pulled apart for access to the interior of the bag.
Although flexible zippers of this variety are quite popular, they do not always prevent the inadvertent or unwelcome opening of a bag or package within the store, and various additions have been made to provide tamper-evident seals which would reveal when it has been opened prior to purchase.
U.S. Pat. No. 5,425,825 to Rasko and Share, which is commonly assigned with the present application and which is incorporated herein by reference, shows and provides a solution to these problems in the form of an improved tamper-evident, non-reclosable peel seal suitable for use with reclosable plastic zippers in plastic bags and other packages to provide a hermetic seal until the peel seal is opened for the first time, and to provide a peel seal which is non-reclosable after being opened.
More specifically, in the invention shown in U.S. Pat. No. 5,425,825, reclosable plastic bags and packages are assembled using two interlocking rib and groove members which reclosably seal the plastic bag or package. In the process by which the reclosable plastic bags and packages are assembled, a strip-like area adjacent and parallel to one of the two interlocking rib or groove members is continuously given a treatment, for example, a flame or corona discharge treatment, to cause an adhesive to preferentially adhere to the treated area. The adhesive, which is applied to the treated area to form the peel seal, is retained on the treated area, rather than on the opposed interlocking rib or groove member not so treated, when the peel seal is broken for the first time. Thereafter, the peel seal remains broken, as the adhesive does not have an affinity for the untreated plastic of the opposite rib or groove number once it has been separated therefrom.
U.S. Pat. No. 5,435,864 to Machacek and Share, which is also commonly assigned with the present application and which is also incorporated herein by reference, shows and provides an alternate solution to the same problems, wherein the adhesive is coextruded onto a strip-like area adjacent and parallel to one of the two interlocking rib or groove members of the interlockable zipper profile. In this instance, the coextrusion causes the adhesive to preferentially adhere to the strip-like area, where the flame or corona discharge treatment did above. The adhesive is retained on that area when the peel seal is broken for the first time. As above, the peel seal remains broken, after it is broken for the first time, as the adhesive does not have an affinity for the plastic of the opposite rib or groove member once it has been separated therefrom.
Peel seals are also disclosed in U.S. Pat. Nos. 4,925,318; 4,969,967; and 5,188,461. Each of these patents shows a package having a closure area comprising first and second opposed surfaces. Profiled portions, adapted to be releasably interengaged to permit connection and disconnection of the opposed surfaces, are secured to and extend over each of the opposed surfaces. The profiled portions are each formed integrally with an outer layer of a strip material secured to the associated one of the opposed surfaces. The outer layer of the strip material is formed of a material well-suited for forming a peel-seal weld with the other opposed surface of the package, such as a portion of the outer layer of the opposing strip material. The profiled portions themselves, then, are formed from the peel-seal material. The outer layer of each strip material is secured to the one of the first and second opposed surfaces via a base layer of the strip material to which the outer layer is secured by means of a non-peel-seal type connection. The profile portions, being formed from a peel-seal material, are frequently damaged during the peel-seal welding process, or during the opening of the peel seal when the package is initially opened.
While the inventions shown in U.S. Pat. Nos. 5,425,825 and 5,435,864 have met with considerable success, the need for a tamper-evident, non-reclosable peel seal which would give a clear indication of the integrity thereof upon visual inspection has recently arisen. In this regard, it has proven to be difficult to determine upon a quick visual inspection whether the peel seals shown in the above-noted U.S. patents are sealed or broken. The present invention provides a tamper-evident, non-reclosable peel seal, which gives a positive indication of having been broken when a package is first opened, and which is non-reclosable after being first opened.